> 1. Text windows sometimes get black "garbage" on the background that > refuses to go, even if text is scrolled over it. > The size of the "garbage" is about 1 character, and looks like an > "island". That is, neither meaningful symbol, nor random pattern.
There are known race conditions in the soft cursor code (not just on the pi). Could the black island be a "mouse dropping"? > 2. When writing large files to an USB memory stick FAT file system (say, > a large TAR archive), the mount is lost, leading to a truncated file. Try putting the memory stick on a powered usb hub and see if that works better.
